Surgically implanted cardiac pacing systems, such as pacemakers and defibrillators, play an important role in the treatment of heart disease. In the 50 years since the first pacemaker was implanted, technology has improved dramatically, and these systems have saved or improved the quality of countless lives. Pacemakers treat slow heart rhythms by increasing the heart rate or by coordinating the heart's contraction for some heart failure patients. Implantable cardioverter-defibrillators stop dangerous rapid heart rhythms by delivering an electric shock.
Cardiac pacing systems typically include a timing device and a lead, which are placed inside the body of a patient. One part of the system is the pulse generator containing electric circuits and a battery, usually placed under the skin on the chest wall beneath the collarbone. To replace the battery, the pulse generator must be changed by a simple surgical procedure every 5 to 10 years. Another part of the system includes the wires, or leads, which run between the pulse generator and the heart. In a pacemaker, these leads allow the device to increase the heart rate by delivering small timed bursts of electric energy to make the heart beat faster. In a defibrillator, the lead has special coils to allow the device to deliver a high-energy shock and convert potentially dangerous rapid rhythms (ventricular tachycardia or fibrillation) back to a normal rhythm. Additionally, the leads may transmit information about the heart's electrical activity to the pacemaker.
For both of these functions, leads must be in contact with heart tissue. Most leads pass through a vein under the collarbone that connects to the right side of the heart (right atrium and right ventricle). In some cases, a lead is inserted through a vein and guided into a heart chamber where it is attached to the heart. In other instances, a lead is attached to the outside of the heart. To remain attached to the heart muscle, most leads have a fixation mechanism, such as a small screw and/or hooks at the end.
Within a relatively short time after a lead is implanted into the body, the body's natural healing process forms scar tissue along the lead and possibly at its tip, thereby fastening it even more securely in the patient's body. Leads usually last longer than device batteries, so leads are simply reconnected to each new pulse generator (battery) at the time of replacement. Although leads are designed to be implanted permanently in the body, occasionally these leads must be removed, or extracted. Leads may be removed from patients for numerous reasons, including but not limited to, infections, lead age, and lead malfunction.
Removal or extraction of the lead may be difficult. As mentioned above, the body's natural healing process forms scar tissue over and along the lead, and possibly at its tip, thereby encasing at least a portion of the lead and fastening it even more securely in the patient's body. In addition, the lead and/or tissue may become attached to the vasculature wall. Both results may, therefore, increase the difficulty of removing the leads from the patient's vasculature.
A variety of tools have been developed to make lead extraction safer and more successful. Current lead extraction techniques include mechanical traction, mechanical devices, and laser devices. Mechanical traction may be accomplished by inserting a locking stylet into the hollow portion of the lead and then pulling the lead to remove it. An example of such a lead locking device is described and illustrated in U.S. Pat. No. 6,167,315 to Coe et al., which is incorporated herein by reference in its entirety for all that it teaches and for all purposes.
A mechanical device to extract leads includes a flexible tube called a sheath that passes over the lead and/or the surrounding tissue. The sheath typically may include a cutting blade, such that upon advancement, the cutting blade and sheath cooperate to separate the scar tissue from other scar tissue including the scar tissue surrounding the lead. In some cases, the cutting blade and sheath may also separate the tissue itself from the lead. Once the lead is separated from the surrounding tissue and/or the surrounding tissue is separated from the remaining scar tissue, the lead may be inserted into a hollow lumen of the sheath for removal and/or be removed from the patient's vasculature using some other mechanical devices, such as the mechanical traction device previously described in U.S. Pat. No. 8,961,551 to Taylor, which is hereby incorporated herein by reference in its entirety for all that it teaches and for all purposes. An example of such a such device and a method used to extract leads is described and illustrated in U.S. Pat. No. 5,651,781 to Grace, which is incorporated herein by reference in its entirety for all that it teaches and for all purposes.
Examples of a laser catheter assembly or laser sheaths that may be used for removing a surgically implanted lead is a coronary laser atherectomy catheter by the Spectranetics Corporation under the trade names SLSII™ and GlideLight™. At the distal end, such catheters include multiple fiber optic laser emitters that surround a lumen. As the fiber optic laser emitters cut the tissue surrounding the lead, the sheath slides over the lead and surrounding tissue, which enter the lumen.
Lead extraction is generally a very safe procedure. However, as with any invasive procedure, there are potential risks. For example, while using any of the tools discussed above to remove a lead, the tool may accidentally pierce, cut, or perforate the vein or artery through which the tool is traveling, thereby allowing blood to escape the patient's vascular system. The rate at which blood escapes may be high if the accidental opening is created close to the patient's heart. Accordingly, a clinician must address the situation quickly to mitigate the amount of blood that escapes from the patient, thereby minimizing potential long-term harm to the patient.